This invention relates to bag opening and closing machines, the bags usually but not necessarily being plastic bags.
Machines for opening and closing bags are of course well known, see for example U.S. Pat. No. 4,124,966 (Wilson) issued Nov. 14, 1978 and U.S. Pat. No. 4,198,800 (Wilson) issued Apr. 22, 1980, the contents of these patents being hereby incorporated herein by reference. Such machines open plastic bags one at a time, fill the open bag with the necessary contents and then close the bag. However, especially with plastic bags, known machines do not open the bags as effectively as desired.
It is therefore an object of the invention to provide a bag opening and closing machine which has a more effective opening mechanism.
According to one aspect of the invention, a method of opening and closing a bag having a front and a rear and an opening at the top includes feeding the bag to a machine which:
a) holds an upper end of the front of the bag,
b) moves the upper end of the rear of the bag rearwardly to partially open the bag,
c) clamps each opposite side of the bag while the bag is in the partially open configuration, and
d) moves the clamped opposite sides of the bag and the rear of the bag rearwardly to a fully open position.
The bag may have a reclosable seal which remains in a closed configuration when the bag has been partially opened and which is opened by a plunger moving into the bag when the bag is being fully opened.
Each side of the body may be clamped by a clamping finger which moves into the bag adjacent the side thereof. Alternatively, each side of the body may be clamped between clamping jaws outside the bag.
According to another aspect of the invention, a bag opening and closing machine for bags having a front and rear and an opening at the top has:
a holder for holding an upper end of the front of the bag,
means for moving an upper end of the rear of the bag rearwardly to partially open the bag,
means for clamping each opposite side of the bag while the bag is in the partially open configuration, and
means for moving the clamped sides of the bag and the front of the bag rearwardly to a fully open position.